Attempts to substitute polyvinyl chloride (PVC) with other materials are actively underway in a variety of industries. However, development of proper substitutes is limited due to flame retardancy, etc. as advantages of polyvinyl chloride. In particular, in preparing electric wires such as cables, it is not easy to realize flame retardancy of polyvinyl chloride using a substitute for polyvinyl chloride.
Regulations regarding flame retardancy are based on UL (Underwriters Laboratories) standards, and, in preparing a resin composition, particularly a thermoplastic resin composition, having suitable flame retardancy satisfying UL standards, a halogen-based flame retardant and a flame retardant are generally kneaded in a thermoplastic resin. Polybromodiphenylether, tetrabromobisphenol A, an epoxy compound with a bromine substituent, chlorinated polyethylene, etc. were mainly used as the halogen-based flame retardant. As the flame retardant, antimony-based compounds are used and, thereamong, antimony trioxide and antimony pentoxide are generally used.
As described above, when flame retardancy is provide to a thermoplastic resin by applying a halogen-based flame retardant and antimony-based flame retardant together, excellent flame retardancy is exhibited and a thermoplastic resin composition, which may produce final products nearly without property deterioration, may be prepared. However, upon processing, hydrogen halide gas is generated and thus a mold may be damaged. In addition, upon discarding, dioxin having strong carcinogenicity is discharged from a waste incinerator due to the presence of a halogen compound, thus harmfully affecting the environment and the human body. Furthermore, regulations on use of halogen-based flame retardant resin materials are actively applied in Europe, and thus, development of materials of a flame retardant thermoplastic resin composition not comprising halogen is required.
In order to provide flame retardancy to a thermoplastic resin composition not comprising halogen, aromatic phosphorus-based ester compounds are generally used. When such a phosphorus-based ester compound is applied alone, heat resistance of a thermoplastic resin is decreased and it is difficult to accomplish desired flame retardancy. Accordingly, in order to enhance heat resistance of a thermoplastic resin and provide flame retardancy thereto, a method of applying a phosphoric ester compound blended with polyphenylene ether has been suggested and studied.
In an embodiment, Korean Patent unexamined Publication No. 10-2013-0121152 discloses a polyphenyl ether elastomer composition. The polyphenyl ether elastomer composition comprises 10 to 46 parts by weight of polyphenylether, 3 to 5 parts by weight of polystyrene, 3 to parts by weight of polystyrene having superior impact resistance, 6 to 13 parts by weight of polyolefin elastomer, 13 to 23 parts by weight of a hydrogenated styrene-butadiene block copolymer, 6 to 16 parts by weight of low-density polyethylene, 5 to 8 parts by weight of a low-density polyethylene graft polystyrene copolymer and 18 to 20 parts by weight of a phosphate flame retardant. In addition, Korean Patent unexamined Publication No. 10-2010-0017356 discloses a flame retardant thermoplastic composition and a product comprising the same. The flame retardant thermoplastic composition comprises poly(arylene ether), block copolymer, liquid polyolefin and a flame retardant additive. The flame retardant additive composition comprises phosphate selected from the group consisting of metal hydroxide, organic phosphate and melamine phosphate, melamine pyrophosphate, melamine orthophosphate, melem polyphosphate, melam polyphosphate, diammonium phosphate, monoammonium phosphate, amide phosphate, melamine polyphosphate, ammonium polyphosphate, amide phosphate and a combination of two or more thereof.
Poly arylene ether comprising the polyphenylene ether is an amorphous resin and has advantages such as superior flame retardancy, insulating properties, heat resistance, rigidity, etc. poly arylene ether modified from the poly arylene ether has substantial advantages in regard to flame retardancy. However, since poly arylene ether has high processing temperature, flame retardant types which may be used are greatly limited. In addition, when a flame retardant is added, in an amount greater than a certain range, to a thermoplastic resin composition comprising the polyphenylarylene ether, there are problems in dispersion of a flame retardant upon processing to electric wires such as cables, and a flame retardant is protruded to a surface of a product that is processed and molded, thereby deteriorating appearance and quality of the product. Accordingly, the total amount of a flame retardant added is limited. In particular, upon extrusion, various problems related to appearance are more likely to occur.
Although various olefin materials are used, it is still difficult to overcome the limitations described above. When general polypropylene and polyethylene based materials are used, various properties in regard to cable extrusion can be satisfied, but hardness increases and cable flexibility is negatively affected.
Therefore, there is still a need for development of a flame retardant thermoplastic resin composition that is suitable for preparation of an electric wire, etc. by addressing conventional problems and enhancing extrudability of a resin composition without decreasing flame retardancy of the resin composition.